A gas magnetic resonance method for rapid measurement of pulmonary gas exchange function

Abstract

The application discloses a gas magnetic resonance method for rapid measurement of lung gas exchange function, and utilizes a SA-CSIR pulse sequence to collect hyperpolarized 129 Xe magnetic resonance spectrum data; when hyperpolarized 129 Xe signals exist in three magnetic resonance signals in the lung of a subject, a relationship between signal strength of a plasma signal and exchange time t and a relationship between signal strength of a red blood cell signal and exchange time t are constructed based on a gas-blood exchange model proposed in the application, and finally, gas exchange function parameters of the lung of the subject are extracted through fitting; the application can acquire data of multiple exchange time points in a single scan, significantly shortens data acquisition time, improves sampling speed, and realizes rapid evaluation of lung gas exchange function; compared with a traditional CSSR technology, the application method can obtain a higher signal-to-noise ratio at a small exchange time, thereby improving evaluation accuracy.

Description

Technical Field

[0001] This invention belongs to the field of gas magnetic resonance technology, specifically relating to a gas magnetic resonance method for rapid measurement of pulmonary gas exchange function, which is suitable for rapid measurement of pulmonary gas exchange function parameters. Background Technology

[0002] In recent years, hyperpolarization 129 Xe magnetic resonance imaging technology has shown significant potential in the assessment of pulmonary gas exchange function. Due to hyperpolarization... 129 Xe magnetic resonance imaging's solubility and chemical sensitivity in lung tissue and blood, hyperpolarization 129 Xe provides important information about the microenvironment of pulmonary gas-blood exchange. Among these, the Chemical Shift Saturation Recovery (CSSR) method analyzes the dissolved substances in erythrocytes and lung tissue / plasma. 129 By restoring the Xe signal curve and fitting it to a gas exchange model, an effective approach is provided for assessing pulmonary gas exchange function.

[0003] However, CSSR technology has some limitations in practical applications. CSSR technology uses the Saturation Recovery (SR) method, which first saturates the dissolved state using a 90° pulse. 129 The Xe signal was then allowed to recover from zero, and magnetic resonance signals were acquired after a period of exchange (Magn Reson Med. 2003; 50(6):1170-9.). Since CSSR requires data acquisition at multiple exchange time points to obtain the signal recovery curve, and the waiting exchange time significantly reduces time efficiency, the overall sampling time is relatively long (NMR in Biomedicine. 2017; 30(8):12.). Furthermore, at small exchange time points, the dissolved state obtained by CSSR... 129 Xe has a relatively low signal-to-noise ratio in its magnetic resonance imaging (MRI) (Magn Reson Med. 2013; 69(3): 884-90.). These limitations restrict the application of CSSR technology in the rapid assessment of pulmonary gas exchange function and in the local visualization assessment.

[0004] Theoretically, changing the 90° pulse in CSSR technology to a 180° pulse and reversing the magnetization vector (let's say the total signal strength is M) from the +z axis to the -z axis would allow the signal to recover from -M instead of 0, theoretically resulting in a stronger signal at smaller exchange time points. Furthermore, by continuously exciting data at small angles, distributing the data from multiple exchange time points of CSSR across different times within a single scan, the sampling speed could theoretically be significantly improved. While this optimization approach is feasible, no publicly available technology or research has yet demonstrated its specific implementation and effectiveness. Similarly, modifications to the CSSR sequence also affect the dissolved state. 129 The Xe signal recovery process involves factors such as the change in initial conditions caused by the 180° pulse, the partial saturation effect caused by continuous small angles, the slowed recovery rate, and the blood flow effect before the 180° pulse. Existing gas-blood exchange models are not applicable to this method. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems in the prior art by providing a gas magnetic resonance method for rapid measurement of pulmonary gas exchange function.

[0006] The above-mentioned objectives of the present invention are achieved by the following technical means:

[0007] A gas magnetic resonance method for rapid measurement of pulmonary gas exchange function includes the following steps:

[0008] Step 1: Acquire hyperpolarization of the subject's lungs using SA-CSIR pulse sequences. 129 Xe magnetic resonance spectral data;

[0009] Step 2: Construct the relationship between signal intensity and exchange time t of lung tissue / plasma signals S′ TP (t), constructing the relationship between the signal intensity of erythrocyte signals and the exchange time t. RBC (t);

[0010] For hyperpolarization 129 After peak fitting processing, gaseous Xe magnetic resonance spectroscopy data were extracted. 129 Xe signal and dissolved state 129 The peak areas of the Xe signal in erythrocyte and lung tissue / plasma signals were obtained, and the signal intensities of lung tissue / plasma and erythrocyte signals at various exchange times t were acquired. These signal intensities were then substituted into the relationship S′ between the signal intensity of lung tissue / plasma and exchange time t. TP (t) and the relationship between the signal intensity of red blood cell signals and exchange time t.RBC In (t), nonlinear fitting is performed to obtain the normalization factor b, the saturation inversion efficiency β, and the gas-blood exchange time constant τ under continuous small-angle radiofrequency pulses. Furthermore, the alveolar surface area-to-volume ratio S is calculated. A / V g and 129 The switching time constant T of the Xe signal.

[0011] As described above, step 1 includes the following steps:

[0012] Step 1.1: The subject is fixed on the MRI scanning table and fitted with a lung support belt. 129 The Xe imaging coil enters the magnet and is drawn into hyperpolarized... 129 Hold your breath after consuming Xe gas;

[0013] Step 1.2: The SA-CSIR pulse sequence first introduces the dissolved state... 129 The frequency center of the Xe signal is set to the RF center of each highly selective RF pulse, and then the RF pulse is applied.

[0014] Applying the radio frequency pulse in step 1.2 as described above includes:

[0015] The SA-CSIR pulse sequence first uses a 90° radio frequency pulse to saturate the dissolved state. 129 The Xe signal is subjected to gradient destruction, followed by dissolution. 129 Saturation recovery time t of Xe signal inv During the period of waiting for the dissolved state 129 Xe signal recovery, in the dissolved state 129 After the Xe signal is recovered, a 180° radio frequency pulse is used to restore the recovered dissolved state. 129 The Xe signal is inverted, and after a time td following the inversion, a small-angle radio frequency pulse with a flip angle of α is applied to the dissolved state. 129 The Xe signal is used for excitation, followed by the application of a small-angle radiofrequency pulse with a flip angle of α at equal repetition times TR, until the set number of repetitions is reached. The hyperpolarization of the subject's lungs is continuously acquired using the small-angle radiofrequency pulses. 129 Xe magnetic resonance spectroscopy data.

[0016] As described above, the relationship between the signal intensity of the lung tissue / plasma signal and the exchange time t in step 2 is S′ TP (t) is based on the following formula:

[0017] S′ TP (t)=S d1 (t)+(1-η)S d2m ′(t)

[0018] In the formula, S d1(t) represents the dissolved state in the blood exchange membrane. 129 The relationship between the signal strength of the Xe signal and the exchange time t, where η is the signal strength of the Xe signal in red blood cells. 129 The signal strength of Xe signals accounts for a significant portion of all blood plasma. 129 The proportion of the signal strength of the Xe signal, S d2m ′(t) represents the final dissolved state within the pulmonary blood vessels. 129 The relationship between the signal strength of the Xe signal and the switching time t;

[0019]

[0020] In the formula, b is the normalization factor, δ is the thickness of the gas-blood exchange membrane, d is the thickness of the lung septum, β is the saturation reversal efficiency, n is the cumulative parameter, odd is the odd parameter, and τ is the gas-blood exchange time constant under continuous small-angle radiofrequency pulses.

[0021]

[0022] In the formula, t X For the time it takes for blood to stay in the lungs, t inv Let T be the saturation recovery time. 129 The switching time constant of the Xe signal.

[0023] As described above, the relationship between the signal intensity of the erythrocyte signal and the exchange time t in step 2 is S RBC (t) is based on the following formula:

[0024] S RBC (t)=ηS d2m ′(t).

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 1. This invention can acquire data from multiple exchange time points in a single scan, significantly shortening data acquisition time, improving sampling speed, and enabling rapid assessment of lung gas exchange function.

[0027] 2. With a short exchange time, the method of the present invention can achieve a higher signal-to-noise ratio compared with the traditional CSSR technology, thereby improving the accuracy of the evaluation.

[0028] 3. Optimized gas-blood exchange model of the lungs: This invention proposes a new gas-blood exchange model that is more suitable for SA-CSIR technology, providing a new approach for accurately assessing lung function. Attached Figure Description

[0029] Figure 1 This is a flowchart of the method of the present invention;

[0030] Figure 2This is a schematic diagram of the SA-CSIR pulse sequence in Embodiment 1 of the present invention (RF, G, and ADC represent the radio frequency pulse, damage gradient, and analog-to-digital signal conversion in the SA-CSIR pulse sequence, respectively, t inv It is the saturation recovery time, and TR is the repetition time of continuous excitation by small-angle radio frequency pulses;

[0031] Figure 3 This is a schematic diagram of the gas-blood exchange model in Embodiment 1 of the present invention (Tissue is lung tissue, RBC is red blood cell, Plasma is blood plasma, d is the total thickness of the lung septum, and δ is the thickness of the gas-blood exchange membrane (lung tissue)).

[0032] Figure 4 The dissolved state in Example 1 of the present invention 129 The recovery curve and fitting effect of the Xe signal (where data-TP is the signal intensity of the lung tissue / plasma signal at each exchange time t, data-RBC is the signal intensity of the erythrocyte signal at each exchange time t, and curve-data-TP is the relationship between the signal intensity of the lung tissue / plasma signal and the exchange time t obtained using the gas-blood exchange model proposed in this invention, S′). TP The fitted curve (t), curve-data-RBC is the relationship between the signal intensity of red blood cell signals and the exchange time t obtained using the gas-blood exchange model proposed in this invention. RBC (fit curve of (t)). Detailed Implementation

[0033] To facilitate understanding and implementation of the present invention by those skilled in the art, the present invention will be further described in detail below with reference to embodiments. The embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0034] Example 1:

[0035] A gas magnetic resonance method for rapid measurement of pulmonary gas exchange function includes the following steps:

[0036] In this embodiment, hyperpolarization 129 The Xe signal presents three magnetic resonance signals in the lungs of the subjects: a gaseous signal, a lung tissue / plasma (TP) signal, and a red blood cell signal, as seen in rats and humans.

[0037] Step 1: Acquire hyperpolarization of the subject's lungs using SA-CSIR pulse sequences. 129 Xe magnetic resonance spectral data, specifically including the following steps:

[0038] Step 1.1: The subject is fixed on the MRI scanning table and fitted with a lung support belt. 129The Xe imaging coil enters the magnet and is drawn into hyperpolarized... 129 Hold your breath after consuming Xe gas (xenon).

[0039] Entering the lungs 129 The signal of Xe gas is divided into gaseous state. 129 Xe signal and dissolved state 129 Xe signal;

[0040] Step 1.2: Acquire hyperpolarization of the subject's lungs using SA-CSIR pulse sequences. 129 Xe magnetic resonance spectroscopy data.

[0041] The SA-CSIR pulse sequence first applies the dissolved state 129 The frequency center of the Xe signal is set to the RF center of each highly selective RF pulse, and then highly selective RF pulses are applied to minimize the effect of the SA-CSIR pulse sequence on the gaseous state. 129 The off-resonance effect of the Xe signal, when applied with highly selective radio frequency pulses, specifically involves:

[0042] The SA-CSIR pulse sequence first uses a 90° radio frequency pulse to saturate the dissolved state. 129 The Xe signal is subjected to gradient destruction, followed by dissolution. 129 Saturation recovery time t of Xe signal inv During the period of waiting for the dissolved state 129 Xe signal recovery, in the dissolved state 129 After the Xe signal is recovered, a 180° radio frequency pulse is used to restore the recovered dissolved state. 129 The Xe signal is inverted, and after a time td following the inversion, a small-angle radio frequency pulse with a flip angle of α (flip angle α is less than 15 degrees) is applied to the dissolved state. 129 The Xe signal is used for excitation, followed by the application of a small-angle radio frequency pulse with a flip angle of α at equal repetition times TR, until the set number of repetitions is reached. This small-angle radio frequency pulse sequence is used to control the dissolved state. 129 Xe signal is continuously excited, and hyperpolarization of the subject's lungs is continuously acquired using a small-angle radio frequency pulse bundle. 129 Xe magnetic resonance spectroscopy data to improve sampling speed and signal-to-noise ratio with small exchange times (0-20ms).

[0043] When the subjects were rats, the following parameters were used: saturation recovery time t inv The parameters are set as follows: 100ms, td, 2ms, repetition time TR, 205ppm, 11°, 600ppm, 256 sampling points, and 24 repetitions. For human subjects, the following parameters are used: saturation recovery time t...inv The parameters were set to 200ms, td to 2ms, repetition time TR to 20ms, flip angle α to 11°, radio frequency center to 208ppm, sampling bandwidth to 600ppm, number of sampling points to 256, and repetition count to 24. For other animals with three MRI signals in the lungs, the parameters need to be determined based on the dissolved state. 129 The signal recovery rate and dissolved state of the Xe signal 129 The chemical shift of the Xe signal is adjusted accordingly.

[0044] Step 2: Based on the gas-blood exchange model proposed in this invention, construct the relationship S′ between the signal intensity of lung tissue / plasma signals and the exchange time t. TP (t) and the relationship between the signal intensity of red blood cell signals and exchange time t. RBC (t); for hyperpolarization 129 After peak fitting processing, gaseous Xe magnetic resonance spectroscopy data were extracted. 129 Xe signal and dissolved state 129 The peak areas of the Xe signal in erythrocyte and lung tissue / plasma signals were obtained, and the signal intensities of lung tissue / plasma and erythrocyte signals at various exchange times t were acquired. These signal intensities were then substituted into the relationship S′ between the signal intensity of lung tissue / plasma and exchange time t. TP (t) and the relationship between the signal intensity of red blood cell signals and exchange time t. RBC In (t), nonlinear fitting is performed to obtain the normalization factor b, the saturation inversion efficiency β, and the gas-blood exchange time constant τ under continuous small-angle radiofrequency pulses. Furthermore, the alveolar surface area-to-volume ratio S is calculated. A / V g and 129 The switching time constant T of the Xe signal is as follows:

[0045] like Figure 3 As shown, the gas-blood exchange model in this invention simplifies the gas-blood exchange region (i.e., the pulmonary septum, with a thickness of d) into a structure including lung tissue (i.e., the gas-blood exchange membrane, with a thickness of δ) and pulmonary vessels (with a thickness of d-2δ, including plasma and red blood cells). 129 Xe signals diffuse from the alveoli into the gas-blood exchange area, while plasma and red blood cells in the pulmonary vessels flow out of the gas-blood exchange area.

[0046] Step 2.1: Based on the novel gas-blood exchange model proposed in this invention, the normalized dissolved state is obtained. 129 The relationship between the signal strength of the Xe signal and the switching time t, S(t), specifically includes the following process:

[0047] Neglecting blood flow, according to Fick's second law, the dissolved state... 129 The density M of Xe d (x,t) is related to time t (exchange time in this embodiment) and distance x (dissolved state in this embodiment). 129 The relationship between Xe and the distance to the interface (between alveoli and lung tissue) is based on the following formula:

[0048]

[0049] In the formula, D represents the dissolved state. 129 The diffusion coefficient of the Xe signal;

[0050] Due to dissolved state 129 Saturation recovery time t of Xe signal inv Long enough and for dissolved state 129 The Xe signal uses a 180° radio frequency pulse, in a dissolved state. 129 The Xe signal has essentially reached a steady state, therefore the dissolved state 129 The density M of Xe d The initial condition M of (x,t) d (x,0) can be equivalently viewed as:

[0051] M d (x,0)=-λM f ,x∈(0,d) (2)

[0052] In the formula, d represents the thickness of the pulmonary septum, and λ represents... 129 The solubility of Xe, M f This refers to the free diffusion of gaseous substances within the alveoli. 129 The density of Xe;

[0053] And because of the dissolved state 129 The density M of Xe d Boundary condition M of (x,t) d (0,t) is:

[0054] M d (0,t)=M d (d,t)=λM f (3)

[0055] By combining the initial and boundary conditions, equation (1) is solved to obtain the solution in the dissolved state. 129 When the distance between Xe and the interface between the alveoli and lung tissue is x, the dissolved state 129 The density M of Xe d The relationship between (x,t) and the exchange time t:

[0056]

[0057] In the formula, n is the cumulative parameter, odd represents the odd number of parameters, and T represents... 129 The switching time constant of the Xe signal, 129 The switching time constant T of the Xe signal is based on the following formula:

[0058]

[0059] Furthermore, after continuous excitation at a small angle, equation (4) is corrected to equation (6):

[0060]

[0061] In the formula, β represents the saturation inversion efficiency, and τ represents the gas-blood exchange time constant under continuous small-angle radio frequency pulses. For the SA-CSIR pulse sequence, the relationship between T and τ is:

[0062] T=(β-1)τ (7)

[0063] Use gaseous state 129 Xe signal for dissolved state 129 The Xe signal is normalized to obtain the relationship S(x,t) between the normalized dissolved state signal and the exchange time t and the distance x at the interface between the alveoli and lung tissue:

[0064]

[0065] In the formula, S A / V g S represents the surface area to volume ratio of alveoli. A V represents the surface area of ​​the alveoli. g This indicates the volume of the alveoli.

[0066] Integrating S(x,t) over a distance x∈(0,d) yields the normalized dissolved state. 129 The relationship between the signal strength of the Xe signal and the switching time t, S(t):

[0067]

[0068] In the formula, the normalization factor b is based on the following formula:

[0069]

[0070] Step 2.2: Construct the dissolved state in the gas-blood exchange membrane based on the novel gas-blood exchange model proposed in this invention. 129 The relationship between Xe signal intensity and exchange time t, and the dissolved state in pulmonary blood vessels. 129The relationships between the signal intensity of Xe signals and exchange time t, the signal intensity of lung tissue / plasma signals and exchange time t, and the signal intensity of erythrocyte signals and exchange time t are specifically included in the following processes:

[0071] Based on such Figure 3 The simplified structure of the gas-blood exchange region shown is used to expand and analyze formula (9), yielding the dissolved state in the gas-blood exchange membrane. 129 The relationship between the signal strength of Xe signal and the switching time t S d1 (t):

[0072]

[0073] It can also obtain the dissolved state within the pulmonary blood vessels 129 The relationship between the signal strength of Xe signal and the switching time t S d2 (t):

[0074]

[0075] S d2 (t) represents the saturation recovery time t without considering blood flow and the effect of the 180° radiofrequency pulse. inv The blood that has already flowed through the gas exchange area 129 Dissolved state in pulmonary blood vessels during the reversal of Xe signaling 129 The relationship between the signal strength of the Xe signal and the switching time t.

[0076] Next, we consider the blood flow situation. Incorporating blood flow into the analysis, we need to further correct formula (12). The dissolved state in the pulmonary vessels under blood flow after correcting formula (12) is obtained. 129 The relationship between the signal strength of Xe signal and the switching time t S d2m (t):

[0077]

[0078] In the formula, t X It indicates the blood residence time in the lungs, which is the average time it takes for red blood cells to pass through the gas exchange area.

[0079] Considering the effect of the 180° radio frequency pulse in the SA-CSIR pulse sequence on the saturation recovery time t inv The blood that has already flowed through the gas exchange area 129 The reversal effect of Xe signaling requires further modification of formula (13), and the final dissolved state in the pulmonary blood vessels obtained after modification is... 129 The relationship between the signal strength of Xe signal and the switching time t S d2m ′(t):

[0080]

[0081] The reason why a constant T is used instead of a constant τ in the third term of formula (14) is because at the saturation recovery time t inv There is no continuous small-angle excitation effect inside.

[0082] Suppose that red blood cells 129 The signal strength of Xe signals accounts for a significant portion of all blood plasma. 129 If the weight of the Xe signal intensity is η, then the relationship between the signal intensity of the lung tissue / plasma signal and the exchange time t is S′. TP The relationship between (t) and the signal intensity of erythrocyte signals and exchange time t. RBC (t) are respectively:

[0083] S′ TP (t)=S d1 (t)+(1-η)S d2m ′(t) (15)

[0084] S RBC (t)=ηS d2m ′(t) (16)

[0085] Step 2.3: The hyperpolarization data collected in Step 1.2... 129 After peak fitting processing of the Xe magnetic resonance spectral data, the gaseous phase was extracted. 129 Xe signal and dissolved state 129 The peak area of ​​the Xe signal in erythrocyte and plasma signals. Next, using gaseous... 129 The signal intensity of the Xe signal is normalized to obtain the signal intensity of the lung tissue / plasma signal and the signal intensity of the red blood cell signal at each exchange time t. The obtained signal intensities of the lung tissue / plasma signal and the red blood cell signal at each exchange time t are substituted into formulas (15) and (16), respectively. Through nonlinear fitting, the signal intensities of b, t X The six gas exchange function parameters, including β, τ, and η, are used to calculate T by substituting β and τ into formula (7), then d by substituting T into formula (5), and finally S by substituting b and d into formula (10). A / V g , obtain S A / V g The two gas exchange function parameters are T and T.

[0086] A gas magnetic resonance imaging device for rapid measurement of pulmonary gas exchange function, comprising:

[0087] The gas exchange function parameter calculation module is used to implement step 2 above: constructing the relationship S′ between the signal intensity of lung tissue / plasma signals and the exchange time t. TP (t), constructing the relationship between the signal intensity of erythrocyte signals and the exchange time t. RBC (t);

[0088] For hyperpolarization 129 After peak fitting processing, gaseous Xe magnetic resonance spectroscopy data were extracted. 129 Xe signal and dissolved state 129 The peak areas of the Xe signal in erythrocyte and lung tissue / plasma signals were obtained, and the signal intensities of lung tissue / plasma and erythrocyte signals at various exchange times t were acquired. These signal intensities were then substituted into the relationship S′ between the signal intensity of lung tissue / plasma and exchange time t. TP (t) and the relationship between the signal intensity of red blood cell signals and exchange time t. RBC In (t), nonlinear fitting is performed to obtain the normalization factor b, the saturation inversion efficiency β, and the gas-blood exchange time constant τ under continuous small-angle radiofrequency pulses. Furthermore, the alveolar surface area-to-volume ratio S is calculated. A / V g and 129 The switching time constant T of the Xe signal.

[0089] A terminal, comprising a processor and a storage medium;

[0090] The storage medium is used to store instructions;

[0091] The processor is used to perform step 2 according to the instructions.

[0092] A computer-readable storage medium having a computer program stored thereon that, when executed by a processor, implements step 2.

[0093] Example 2:

[0094] A gas magnetic resonance method for rapid measurement of pulmonary gas exchange function includes the following steps:

[0095] Step 1: Acquire hyperpolarization of the subject's lungs using SA-CSIR pulse sequences. 129 Xe magnetic resonance spectroscopy data.

[0096] In this embodiment, hyperpolarization 129In cases where the Xe signal exists as two magnetic resonance signals in the lungs of a subject, namely a gaseous signal and a dissolved signal (DP), such as in mice, rabbits, and other animals.

[0097] In this embodiment, based on the animal's 129 The signal recovery rate and chemical shift of the Xe signal are used to adjust the corresponding parameters. For example, for mice, the radiofrequency pulse center should be set to 197 ppm, and the saturation recovery time t of the mouse should be... inv The settings for repetition time TR, flip angle α, sampling bandwidth, number of sampling points, and number of repetitions are the same as those for the rats in Example 1.

[0098] Step 2: Construct a dissolved state based on the gas-blood exchange model proposed in this invention. 129 The relationship between the signal strength of Xe and the switching time t, and the hyperpolarization acquired in step 1.2. 129 The normalized dissolved-state signal intensity at each exchange time t was obtained from the Xe magnetic resonance spectroscopy data. Finally, the gas exchange function parameters of the subject's lungs were extracted by fitting, specifically:

[0099] Step 2.1, the same as step 2.1 in Example 1, is derived based on the new gas-blood exchange model proposed in this invention to obtain the normalized dissolved state. 129 The relationship between the signal strength of the Xe signal and the switching time t, S(t);

[0100] Step 2.2: Construct a dissolved state based on the novel gas-blood exchange model proposed in this invention. 129 The relationship between the signal strength of Xe and the switching time t is as follows:

[0101] Since only gaseous and dissolved signals exist in the lungs of the subject in this embodiment, only the dissolved signal needs to be obtained. 129 The relationship between the signal strength of Xe and the switching time t is as follows:

[0102] Incorporating blood flow into the analysis, formula (9) is corrected to obtain the dissolved state under blood flow conditions. 129 The relationship between the signal strength of Xe and the switching time t, S′(t):

[0103]

[0104] Considering the effect of the 180° inversion pulse in the SA-CSIR pulse sequence on the saturation recovery time t inv The blood that has already flowed through the gas exchange area 129 The reversal effect of Xe requires modification of formula (17) to obtain the final dissolved state. 129The relationship between the signal strength of Xe and the switching time t, S″(t):

[0105]

[0106] Step 2.3: The hyperpolarization data collected in Step 1.2... 129 After peak fitting processing of the Xe magnetic resonance spectral data, the gaseous phase was extracted. 129 Xe signal and dissolved state 129 The peak area of ​​the Xe signal. Then, by using gaseous... 129 The peak area of ​​the Xe signal is related to the dissolved state. 129 The Xe signal is normalized to obtain the signal intensity of the dissolved state signal at each normalized exchange time t. The obtained signal intensity of the dissolved state signal at each normalized exchange time t is substituted into formula (18), and the signal intensity including b and t is extracted through nonlinear fitting. X The four gas exchange function parameters, including β, τ, etc., are used to calculate T by substituting β and τ into formula (7), then d by substituting T into formula (5), and finally S by substituting b and d into formula (10). A / V g , obtain S A / V g The two gas exchange function parameters are T and T.

[0107] A gas magnetic resonance imaging device for rapid measurement of pulmonary gas exchange function, comprising:

[0108] The gas exchange function parameter calculation module is used to implement step 2 above: constructing a dissolved state based on the gas-blood exchange model proposed in this invention. 129 The relationship between the signal strength of Xe and the switching time t, and the hyperpolarization acquired in step 1.2. 129 The signal intensity of the dissolved state signal at each exchange time t was obtained from the Xe magnetic resonance spectroscopy data after normalization, and finally the gas exchange function parameters of the subject's lungs were extracted by fitting.

[0109] A terminal, comprising a processor and a storage medium;

[0110] The storage medium is used to store instructions;

[0111] The processor is used to perform step 2 according to the instructions.

[0112] A computer-readable storage medium having a computer program stored thereon that, when executed by a processor, implements step 2.

[0113] It should be noted that the embodiments described in this invention are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains can make various modifications or additions to the described embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A gas magnetic resonance method for rapid measurement of pulmonary gas exchange function, characterized in that, Includes the following steps: Step 1: Acquire hyperpolarization of the subject's lungs using SA-CSIR pulse sequences. 129 Xe magnetic resonance spectral data; Step 2: Construct the relationship between signal intensity and exchange time t of lung tissue / plasma signals. To construct the relationship between the signal intensity of erythrocyte signals and the exchange time t. ; For hyperpolarization 129 After peak fitting processing, gaseous Xe magnetic resonance spectroscopy data were extracted. 129 Xe signal and dissolved state 129 The peak areas of the Xe signal in erythrocyte and lung tissue / plasma signals were determined, and the signal intensities of the lung tissue / plasma and erythrocyte signals at various exchange times t were obtained. These signal intensities were then substituted into the relationship between the lung tissue / plasma signal intensity and the exchange time t. and the relationship between the signal intensity of red blood cell signals and the exchange time t In the process, nonlinear fitting is performed to obtain the normalization factor. saturation inversion efficiency And the gas-blood exchange time constant under continuous small-angle radiofrequency pulses. And further calculate the surface area-to-volume ratio of alveoli. and 129 The switching time constant T of the Xe signal, The relationship between the signal intensity of the lung tissue / plasma signal and the exchange time t in step 2 Based on the following formula: In the formula, Dissolved state in the gas exchange membrane 129 The relationship between the signal strength of the Xe signal and the switching time t For red blood cells 129 The signal strength of Xe signals accounts for a significant portion of all blood plasma. 129 The proportion of the signal strength of the Xe signal, For the final dissolved state within the pulmonary blood vessels 129 The relationship between the signal strength of the Xe signal and the switching time t; The relationship between the signal intensity of the red blood cell signal and the exchange time t in step 2 Based on the following formula: 。 2. The gas magnetic resonance method for rapid measurement of pulmonary gas exchange function according to claim 1, characterized in that, Step 1 includes the following steps: Step 1.1: The subject is fixed on the MRI scanning table and fitted with a lung support belt. 129 The Xe imaging coil enters the magnet and is drawn into hyperpolarized... 129 Hold your breath after consuming Xe gas; Step 1.2: The SA-CSIR pulse sequence first introduces the dissolved state... 129 The frequency center of the Xe signal is set to the RF center of each highly selective RF pulse, and then the RF pulse is applied.

3. The gas magnetic resonance method for rapid measurement of pulmonary gas exchange function according to claim 2, characterized in that, Applying the radio frequency pulse in step 1.2 includes: The SA-CSIR pulse sequence first uses a 90° radio frequency pulse to saturate the dissolved state. 129 The Xe signal is subjected to gradient destruction, followed by dissolution. 129 Saturation recovery time t of Xe signal inv During the period of waiting for the dissolved state 129 Xe signal recovery, in the dissolved state 129 After the Xe signal is recovered, a 180° radio frequency pulse is used to restore the recovered dissolved state. 129 The Xe signal is inverted, and after a time td following the inversion, a small-angle radio frequency pulse with a flip angle of α is applied to the dissolved state. 129 The Xe signal is used for excitation, followed by the application of a small-angle radiofrequency pulse with a flip angle of α at equal repetition times TR, until the set number of repetitions is reached. The hyperpolarization of the subject's lungs is continuously acquired using the small-angle radiofrequency pulses. 129 Xe magnetic resonance spectroscopy data.

4. The gas magnetic resonance method for rapid measurement of pulmonary gas exchange function according to claim 3, characterized in that, Dissolved state in the gas exchange membrane 129 Relationship between signal strength of Xe signal and switching time t Based on the following formula: In the formula, As the normalization factor, The thickness of the gas exchange membrane, This refers to the thickness of the pulmonary septum. For saturation inversion efficiency, n is the accumulation parameter, and odd is the odd number of parameters. The time constant of gas-blood exchange under continuous small-angle radiofrequency pulses; The final dissolved state in the pulmonary blood vessels 129 Relationship between signal strength of Xe signal and switching time t Based on the following formula: In the formula, For the time blood stays in the lungs, Let T be the saturation recovery time. 129 The switching time constant of the Xe signal.

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